floor joists II

[wildwood]

Can't post an answer to your Q below gedg, so here goes.

[wildwood]

You sound like one of those dogmatic people who want to do everything yourself, just like the one my wife is married to. Again, professional advice is needed here. I presume we are talking groundfloor here, and you wish to drill a 4" hole horizontally through one of the joists.
I would get a length of ground treated 4x4 and horizontally support the joist with 18" of this. this support will then be underpinned by the rest of the 4x4 vertically, resting on a concrete base, just like a proper pile. Use dampcoursing to stop moisture creeping up. wedges can be inserted to tighten the support and even out any eventual shinkage or settling.
Ofcourse, this is only what I would do, what you do is entirely up to you.